A little googling told me that in Greece an upward nod/rising the eyebrows now, over 2500 years later, still means "no" and a downward nod still means "yes". Can someone who knows Greek culture confirm this?

Sort of, its very much a Mikrasiatic mannerism though obviously has spread through the mainland along with a few other gestures like a sort of /ts/ sound for no, which is considered very very rude in most countries. It's not that common. I know many Greeks who carry this gesture over to English lol.

But, yeah, this sort of thing is common to Asia in general. Along with, for example, putting your hand out flat towards someone being really offensive and a small host of other gestures which can be misconstrued.

Well it sort of makes sense that it's common in the region of present day Turkey. It's intriguing how far back this kind of thing can go. I wonder if somebody has done systematic research on "historical body linguistics". As a side note, I suspect marital customs (monogamy in the "West", polygamy in the "East") are also extremely old and go back in their respective regions much further than the religions to which they are attributed (i.e. Christianism and Islam).